1. Field of the Invention
This invention relates generally to sewing machines. In particular, it relates to a controller for a two-needle corner sewing machine including a needle bar mechanism capable of sewing either with two needles and with only one of the two needles by stopping the other needle.
2. Background Art
As is taught in the prior art, for example, by Japanese Unexamined Patent Publication No. 55-122590, there is known a means for controlling a type of two-needle corner sewing machine including a needle bar mechanism capable of sewing either with two needles or with only one of the needles, the other being stopped. Shown in FIG. 1 is a two-needle sewing machine 1, specifically the arm bed of the sewing machine, located on a table 2 and powered through a pulley 3. An ordinary needle position detector 4 detects the needle position in order to stop a needle 5 at a lower position. A motor 6 drives the sewing machine 1 through the pulley 3 and is controlled by a pedal 7. Control means 8 controls the sewing machine 1. A lever-like changing means 9 changes the sewing machine 1 to one-needle operation from two-needle operation or conversely to two-needle operation from one-needle operation. The lever-like changing means 9 is rotatably mounted on the sewing machine 1, and is positioned at a neutral position by a neutral return spring (not shown) for a normal operation in which the two-needle mechanism is set. The one-needle mechanism is set when the changing means 9 is rotated to the right or left. The one-needle mechanism for operating the needle 5 on the right side is set when the upper end of the changing means 9 is rotated to the right side against the force of the neutral return spring, and the one-needle mechanism for operating the needle at the left side is set when the upper end of the changing mechanism 9 is rotated to the left side against the neutral return spring. An electromagnet 11 rotates the changing means 9 to the right side, while another electromagnet 12 rotates the changing means 9 to the right side. The magnets 11 and 12 are driven by the control panel 8. A changing means 10 designates the electromagnet 11 or 12 to the driven for a corner sewing operation.
An operating panel 13 sets the number of the different type of the corner portions and the number of the stitches to be sewn in the corner portions since the corner portions are of different types and lengths. As shown in FIG. 2, a number-of-stitches setting means sets the number of stitches to be sewn using one needle at the first corner portion. Additional number-of-stitches setting means 21, 22 and 23 set the numbers of the stitches using only one needle at the second to fourth corner portions. The additional setting means 21, 22 and 23 are constituted of switches. A designating means 24 determines the total operative number of the four number-of-stitches setting means 20 to 23. In this prior art, the designating means 24 is also constituted of a switch.
In the prior art described above, if the sewing pattern shown in FIG. 3 is carried out, the switch of the number-of-stitches setting means 24 shown in FIG. 2 is set to "1" because the number of stitches sewn with one needle is one at the first corner portion (A portion). The number of stitches is duplicated on each side of the corner. Further, the switch 21 in FIG. 2 is set to "3" because the number of stitches with one needle is three at the second corner portion (B portion). Also, the switch 22 is set to "1" for the third corner portion (C portion). For this example, the designating means 24 is set to "3" because the number of corners is three in this example. Further, the changing means 10 is set to the right because all of the one-needle sewing operations are operations with the right needle 5 of the sewing machine 1. Now, the ordinary high speed operation using two needles is carried out before the point 100 in FIG. 3, and is performed by one-directional tread operation of the pedal 7. The needles are stopped at the point 100 in FIG. 3 by returning the pedal 7 to the neutral position.
Next, when a corner sewing signal is generated, the electromagnet 12 operates to rotate the changing means 9 to the right side by the control means 8. Then the control means 8 operates the motor 6 to perform one-needle sewing between the points 100 to 200 during the single period set by the first number-of-stitches setting means 20. The needles are stopped at the point 200. When the direction of the cloth is changed at this point 200 and the pedal 7 is again treaded to the forward direction, one needle sewing is again performed during the single section between the points 200 to 300 set by the first number-of-stitches setting means 20. Then, the control means 8 operates the electromagnet 11 rotating the changing means 9 to the left side, and the sewing is returned to two-needle sewing at the point 300. Two-needle sewing is performed in the section 300 to 400.
When the needles are stopped at the point 400 by positioning the pedal 7 to the neutral position, and the changing means 9 is turned on, sewing is again changed to one-needle sewing, which is performed between the points 400 to 500 during the three periods set by the second number-of-stitches setting means 21. Subsequently, the needle is stopped at the point 500, the direction of the cloth is changed, and then one-needle sewing is performed by the forward direction tread operation of the pedal 7 for the three periods set by the second number-of-stitches setting means 21. Thereafter, the sewing operation is returned to two-needle sewing.
In the C portion shown in FIG. 6, the one-needle sewing is also performed during the single period set by the third number-of-stitches setting means 22.
In the two-needle sewing machine of the prior art, as described above, a bent seam is sewn in the cloth, and the amount of the cloth fed by a cloth feeding mechanism is little because, when the direction of the cloth is changed, a cloth presser is lifted. The cloth presser is moved downward to perform the one-needle sewing after the needles are stopped at the point 200. Therefore, compensation sewing must be performed with an auxiliary switch or the like because the number of the stitches between the points 100 and 200 is different from that of the stitches between the points 200 and 300.
Further, the sewing machine of the prior art has the disadvantage that it cannot be used in case the number of the stitches between the points 100 and 200 must be different form that of the stitches between the points 200 and 300 when a special corner portion is to be sewn.